There are many known methods for applying a texture finish to a drywall surface. For a large area, contractors typically use trailer-mounted spray machines to finish drywall surfaces. These machines have large capacity tanks where powdered material is mixed with water. The material is pumped through a hose to the spray gun. The finish can be varied from fine to heavy by changing tips in the spray gun nozzle, adjusting air pressure, or by changing the viscosity of the texture material. This application is typically done only by a professional at the time of building the structure.
Hopper guns are often used for mid-sized texture jobs and for touch-ups. A hopper is similar to a trailer-mounted machine but on a smaller scale. It uses a portable hopper and compressed air to spray texture on the drywall surface. Changing air pressure and nozzles are also used to achieve desired texture pattern, which requires the applicator to have skill similar to the trailer mounted machine applicator. The use of a compressor or the ability to clean the hopper is sometimes difficult or not possible as electricity and water may not be available. Also, storm water regulations may not permit cleaning the hopper on site. Current aerosol texture spray can technology provides a convenience to the applicator by not having to use a bulky or heavy compressor and clean the hopper texture spray gun after a patch is complete.
Aerosol texture spray cans are primarily designed to apply texture to finish drywall patches in an attempt to match existing wall texture patterns. Current texture spray can technology is accomplished by mixing a propellant and texture together in an aerosol can that is expelled through a dip-tube and then a spray tip. This eliminates the need in dealing with compressors, hoses, cleaning, and other cumbersome equipment for jobs where they are not warranted or feasible. While spray cans are convenient, they have some significant drawbacks.
Current texture spray can technology is accomplished by mixing a propellant and texture together in an aerosol can that is expelled through a dip-tube and then a spray tip.
The current propellant commonly used for this is an aerosol known as DME (Dimethyl ether). Because the propellant and texture are mixed together in the aerosol can, the propellant is part of the liquid that contributes to the flow and viscosity of the texture from the can. When the liquid propellant is expelled or released from the spray can, the gas is designed to expand thus giving the spray velocity or propellant for the material from the can's spray nozzle.
A major disadvantage of combining the texture material and the propellant together is that the propellant is still expanding and escaping from within the textured material once it is applied to the wall patch. This creates what is known in the drywall industry as pin-holing (as seen in FIG. 1). Pin-holing is a negative attribute in professionally applied work and is often unacceptable and the applicator is required to repair the pin-holing to a professional standard. This issue is not able to be resolved by a practical amount of defoamer in the texture material formula.
In addition, because current aerosol spray can technology does not incorporate a “positive” shut-off mechanism at the tip of spray tips, the mixed propellant and texture material continues to build up and flow at the tip of the spray tip as the propellant gas continues to expand within the texture material (as seen in FIG. 2). This causes “spitting” of the texture material once the aerosol valve is activated again (as seen in FIG. 3). The “spitting” of material causes larger spots of texture pattern that are not uniform in pattern. “Spitting” of material is a negative attribute in professionally applied work and is often unacceptable. The professional applicator is often required to repair the non-uniform texture pattern to a professional standard.
Further, the aerosol texture spray can industry trend has been to offer an increasing amount of square footage coverage. This is where more texture material is offered in a single can. Current technology has practical and physical limitations as to the amount of square footage coverage they can offer. A typical aerosol texture spray can that contains increased square footage coverage comes with 25 ounces of texture material plus the appropriate amount of aerosol propellant. This larger texture volume can measure approximately 12 inches in height and weighs approximately 1.5 pounds. In order to further increase square foot coverage by an additional 50% the texture spray can would have to be 18 inches in height and weigh approximately 2.25 pounds. An 18-inch high texture spray can create logistical issues especially on store shelves and is a practical inconvenience for the applicator to use. This also causes increased shipping costs since many spray cans are delivered direct to stores.
In addition, the aerosol texture spray can industry typically utilizes DME (Dimethyl ether). One of the main advantages for its use is that DME is compatible with water-based materials. Because most of the texture materials on the market are water-based, DME mixes well with the texture material in the aerosol can and provides the necessary pressure to achieve the appropriate spray pattern. One of the major disadvantages of DME is that it is highly flammable. The auto ignition temperature of DME is approximately 662° F. Note; the temperature of an idly burning cigarette is over 1000° F. Certain compatible aerosols that mix with the water-based texture materials also contain volatile organic compounds (VOCs) that are not environmentally friendly or healthy for the applicator. Because typical spray can technology mixes the propellant with the texture material in the can to achieve an appropriate spray texture pattern, the choices of propellants are limited as well.
Since the appropriate mixture of DME or suitable propellant must be mixed with the texture material to achieve the required spray pattern, a further disadvantage of current spray can technology is that the mixture of texture material to propellant cannot be adjusted by the applicator. It is a fixed ratio in the aerosol can.
Professional texture hopper guns allow for the amount of texture material to be varied in relation to their air source. This is important when matching the existing texture of a wall while doing repair work. To better match existing textures, professionals often “feather” the texture around the patched area. Feathering is accomplished by keeping the air pressure constant while limiting the amount of texture material that is sprayed from the texture hopper gun so that the edges of the patch have lighter and lighter amounts of texture material towards the outer edges of the patch. This visually blends the new texture subtly with the original texture that was applied at the time of construction so that the patch is less noticeable.
Furthermore, it is common in the texture spray can industry to have a high number of product returns. This is not only inconvenient for the consumer or applicator, but it is costly and time consuming for the stores that sell the aerosol texture spray cans. The high number of returns is due to the nature of the product. Texture material is typically much thicker than paint due to the high solids needed to create the texture pattern. The heavy texture is typically pushed by the propellant through a dip-tube or “feed-tube” that extends down into the can. The heavy bodied texture must then pass through a relatively small valve to the spray tip. This often leads to product malfunctions and clogging. Many times a dried piece of the texture material can clog the spray can valve. Slight activation of the material valve can occur as well during the assembly of the spray can which can cause a small amount of material to become hardened in the valve components. In addition, because the aerosol and material are mixed together, there is a disadvantage in the current technology since there is a limitation on how big the valve openings can be to achieve a desired texture pattern due to the level of propellant needed to create the force to spray.
Thus, there remains a need for a spray apparatus that applies a texture material to a wall, which better represents, and that can better match, the professional textures originally applied to the walls or surfaces when the structure was originally built and that can functionally and practically facilitate additional square foot coverage of the texture material. Consumers and retailers would also benefit from a more reliable product with fewer returns to the store. In addition, there remains a need for an environmentally friendly and a safer, non-flammable texture delivery system that is also more economical and safer to ship and handle.